The present invention relates to a method of evacuating the air when introducing into a sealing-tight tubular body, for example the rigid or semi-rigid body of a receptacle or a distributor, of a lid or seal adapted to slide therein in sealing-tight manner.
The document FR-B-2605983=EP-A-270467=U.S. Pat. No. 4,809,887 describes a method of introducing a sliding piston into a body of a distributor filled with pasty product, in which the sealing-tight lip situated at the front of the piston is contracted by passing through an inlet zone flared according to a transverse relief of minimal diameter which is 0.3 to 1.5 mm smaller than the inside diameter of the said body. This contraction of the lip creates tiny undulations or curling through which the air trapped between the piston and the pasty product can escape and it is necessary that the piston move forward at a speed of at least 40 mm/s for these undulations to persist under the effect of the passage of air.
When the speed of the piston diminishes, the small undulations disappear and the air no longer passes through, so that in practice a small amount of air is occluded, corresponding to the slowing down and stoppage of the piston. Furthermore, the solution of an inner transverse relief is applied above all to tubular bodies of synthetic plastics material and the creation of such a relief by means of an attached foot, although it may well suit other kinds of bodies, is a complication with regard to storage and the series production of distributors.
The Applicants have sought to perfect a solution which avoids such drawbacks.